Portable, handheld work apparatuses such as chain saws, cut-off machines, hedge trimmers, blower apparatuses or the like are usually driven by a combustion engine which on location has to be taken into operation via a starting unit. Prior to the activation of the starting unit, which, for example, can be a pull starter, the combustion engine is placed into a starting mode, that is the fuel supply and the combustion air supply are set correspondingly. This can, for example, be done by adjusting a choke flap or a throttle flap in the intake channel.
When the combustion engine starts after multiple starting strokes, care must be taken that the rotational speed of the combustion engine does not increase above the engaging rotational speed of the clutch in the starting phase, via which clutch the worktool is driven. The clutch, typically a centrifugal clutch, engages above an engaging rotational speed and disengages the worktool from the drive below the engaging rotational speed. In order to ensure that the rotational speed of the combustion engine does not increase above the engaging rotational speed in the starting phase of the combustion engine, a rotational speed lock circuit is provided which holds the current rotational speed of the combustion engine below the engaging rotational speed electronically and preferably forces the current rotational speed below a limit rotational speed of the rotational speed lock circuit.
When the rotational speed lock circuit is switched on, the rotational speed control unit will constantly attempt to keep the rotational speed below the predetermined limit rotational speed of the rotational speed lock circuit via regulator interventions.
For this reason, after the starting phase has run its course, the rotational speed lock circuit has to be switched off so that the operator can use the entire rotational speed range of the combustion engine for the work assignment.